Virtual retinal display with expanded exit pupil

Abstract

A display device is achieved using a simplified optical system which generates an expanded exit pupil without compromising magnification or resolution. Modulated light from a source is converged toward a focal point by an optics subsystem. A scanning subsystem deflects the converging light, and thus the focal point, along a raster pattern to define a curved intermediate image plane. An exit pupil expanding apparatus defines a curved surface which coincides with the curved image plane. Impinging light rays at a given instant in time span a given incidence angle. Exiting light rays span a larger angle. As a result, the exiting light spans a larger surface area of an ensuing eyepiece. In turn an expanded exit pupil occurs beyond the eyepiece. Embodiments of the expanding apparatus include a curved diffractive optical element, fiber optic face plate, lens array and diffuser. The diffractive optical element generates multiple exit pupils, while the other embodiments generate enlarged exit pupils.

What is claimed is: 
     
       1. A scanning display for providing an image in response to an image signal containing image information, comprising: control electronics having an input terminal and an output terminal, the input terminal receiving the image signal, the control electronics being responsive to the image signal to produce a control signal at the output terminal;   an optical source having a signal input coupled to the output terminal of the control electronics, the optical source being responsive to the control signal to output a modulated beam of light along a central path;   a scanning assembly having a beam input positioned to receive the modulated beam of light, the scanning assembly being operative to deflect the received beam of light from the central path through a two dimensional periodic pattern of angles relative to the central path, each angle defining a respective optical path;   imaging optics positioned to intercept the modulated beam of light, the imaging optics having an optical power selected to produce an image location at an image distance along each of the optical paths; and   a diffractive beam expander positioned to intercept the modulated beam of light at the image distance for each of the optical paths, the beam expander producing a plurality of output beams from the modulated beam for each of the optical paths in the periodic pattern of optical paths, each of the output beams being directed along a vector that is a function of the corresponding angle defining its respective optical path.   
     
     
       2. The display of claim 1, in which the optical source comprises a light source and a modulator, wherein the light source generates light and wherein the modulator receives the generated light and the control signal to modulate the generated light in response to the control signal to output the modulated beam of light along the central path. 
     
     
       3. The display of claim 1, in which the optical source comprises a light source which is directly modulated to output the modulated beam of light along the central path. 
     
     
       4. The display of claim 1, in which the optical source outputs a modulated beam of colored light. 
     
     
       5. The display of claim 1, wherein the plurality of output beams define a two dimensional array of output beams. 
     
     
       6. The display of claim 1, further comprising optics receiving the plurality of output beams which couple the output beams to a viewer's eye to generate a plurality of exit pupils. 
     
     
       7. The display of claim 1, further comprising a fiber optic coupling the modulated beam of light from the optical source to the scanning assembly. 
     
     
       8. The display of claim 1, wherein the scanning assembly deflects the received beam of light from the central path along a raster pattern. 
     
     
       9. The display of claim 1, wherein the diffractive beam expander has a curved surface where the beam expander intercepts the modulated beam of light. 
     
     
       10. The display of claim 1, wherein the control electronics decode the received image signal to generate the control signal. 
     
     
       11. The display of claim 1, wherein the optical source, scanning assembly, image optics and beam expander are sized and relatively positioned for mounting relative to a viewer's eye. 
     
     
       12. A scanning display, comprising: a scanning source operative to output a beam of light at a series of different scanned angles;   an exit pupil expander including a plurality of input locations, the exit pupil expander being positioned to receive the beam of light at a respective one of the input locations for each of the different scanned angles, the exit pupil expander being configured at each of the locations to redirect portions of the received beam from each of the scanned angles to a respective set of discrete output angles, wherein the set of output angles for each of the scanned angles includes a plurality of discrete output angles, each discrete output angle being a function of the respective scanned angle; and   imaging optics positioned to receive substantially all of the portions of the beam of light from the exit pupil expander, the imaging optics having a size and optical power selected to form a plurality of discrete exit pupils from the received portions, each exit pupil including light received from substantially all of the sets of output angles.   
     
     
       13. The display of claim 12, in which the scanning source outputs a beam of colored light. 
     
     
       14. The display of claim 12, wherein the scanning source is operative to output a beam of light at a series of different scanned angles occurring in a raster pattern. 
     
     
       15. The display of claim 12, wherein the exit pupil expander has a curved surface spanning the plurality of input locations. 
     
     
       16. The display of claim 12, wherein the scanning source, exit pupil expander and imaging optics are sized and relatively positioned for mounting relative to a viewer's eye. 
     
     
       17. A method of providing an image for viewing by a viewer, comprising the steps of: receiving an image signal containing image information corresponding to the image;   producing a modulated light beam having a modulation corresponding to the image information;   scanning the modulated light beam through a predetermined scan pattern including a sequence of scan angles;   for each of the scan angles, diffracting the scanned beam with an optical element configured to produce a respective set of diffracted beams, each diffracted beam having a respective angle relative to the corresponding scan angle;   directing a first of the diffracted beams in each of the sets to a first common location to produce a first exit pupil, the first exit pupil including light modulated with the image information; and   directing a second of the diffracted beams in each of the sets to a second common location to produce a second exit pupil, the second exit pupil including light modulated with the image information, such that the viewer can perceive the image at either of the first or second common locations.   
     
     
       18. The method of claim 17, wherein the predetermined scan pattern is a raster pattern. 
     
     
       19. The method of claim 17, further comprising the step of receiving the modulated light beam at a curved surface of the optical element, and wherein as the modulated light beam is scanned through the predetermined scan pattern the modulated light beam is scanning along the curved surface. 
     
     
       20. A method of producing a plurality of virtual images perceivable by a viewer, comprising the steps of: modulating a beam of light with image information;   scanning the beam of light through a two dimensional periodic pattern;   dividing the scanned beam of light into a plurality of sub-beams by diffracting the beam of light through a grating; and   for each position in the two dimensional periodic pattern, shaping each of the sub-beams for viewing by the viewer.   
     
     
       21. The method of claim 20, in which the beam of light is colored light. 
     
     
       22. The method of claim 20, in which the two dimensional periodic pattern is a raster pattern. 
     
     
       23. The method of claim 20, in which the step of shaping each of the sub-beams comprises forming a respective exit pupil for each one of a plurality of said sub-beams. 
     
     
       24. The method of claim 20, in which the step of dividing comprises diffracting the beam of light through a curved grating.